The debut of the government's bill on gay marriage - the Marriage (Same Sex Couples) Bill - is this week's biggest Parliamentary event.
My impression is that backbench Conservative support is fading under the glare of opposition from local activists; and when David Burrowes, the MP acting as the unofficial whip against the bill, claims that two thirds of Tory MPs will be unable to support the bill, I don't find that implausible.
MPs report that their postbags bulge with letters from opponents and several Conservatives have told me they fear for the consequences if they support the bill - a possible haemorrhage of activists to UKIP, even murmurings of de-selection. On the other side of the argument the UK Freedom to Marry organisation has been writing to all Conservative Association chairmen in Conservative seats this week.
Some worried MPs will be listening very carefully to what is said by ministers about key issues like whether it can be guaranteed that religious organisations will not be forced to carry out same-sex marriages, against their beliefs, perhaps under human rights legislation.
The level of Conservative opposition can't, strictly, be called a rebellion, because this will be a conscience issue, and the Conservatives (and Labour) will allow their members a free vote. But no-one is under any illusions about how David Cameron would like them to vote. Since most Labour and Lib Dem MPs support the bill, the chances are that it will sail through second reading, although many Conservatives will vote against, because their concern is not issues of detail but the basic principle.
Can there be any link made between voting against this bill, and more general internal Tory dissent? I think there can. The bill has become totemic. It seems to have crystallised concerns about Mr Cameron's social liberalism and his perceived attitude to his own grassroots. The polls suggest that support for UKIP - a party whose rise has alarmed many Conservatives - is based not just on concern about the EU, but on a wider set of complaints and a visceral social conservatism, and this bill could deepen those concerns.
So the list of antis and abstainers will be studied with great interest in the whips' office.
And in a similar vein, keep an eye on what happens with John Baron's ten minute rule bill on an EU referendum on Wednesday...
Here's the run-through of the rest of the week:
On Monday, the Commons meets at 2.30pm for Communities and Local Government questions - which looks like the highlight of a pretty workaday agenda. Then (assuming no statements by ministers or urgent questions) the main debate is on the second reading of the European Union (Approvals) Bill.
This rubber-stamps a series of changes to the operating rules of the EU: everything from allowing an electronic version of the EU's official journal, to establishing a Multiannual Framework for the European Agency for Fundamental Rights for 2013-2017. It didn't generate much excitement passing through the Lords, and I don't anticipate much in the Commons.
Over in the Lords (from 2.30pm) question time ranges across the Royal Navy's rules of engagement for dealing with pirates, affordable homes in rural areas and opt-outs from European Union legislation. Then peers turn to the committee-stage discussion of the Mental Health (Discrimination) (No. 2) Bill - this is the private member's bill pushed through the Commons by the Conservative Gavin Barwell, to abolish various forms of legal discrimination against people who have, or who have had mental health problems - which may prevent them serving as company directors, jurors or even MPs. The bill will be piloted through by the Crossbencher, Lord Stevenson of Coddenham.
That is followed by detailed scrutiny of the Growth and Infrastructure Bill - key issues are around changes to infrastructure planning, and the 2008 Planning Act and Business Rate Revaluation. And there will also be a short debate on the contribution of academies and free schools to educational provision in the United Kingdom.
On Tuesday, the Commons meets at 11.30am for justice questions and then there's a ten minute rule bill from the Conservative Stephen Mosley on Building Regulations (External Retaining and Load-bearing Walls). That is just an appetiser for the Marriage (Same Sex Couples) Bill (see above).
In Westminster Hall, there are a series of backbench debates (from 9.30am) - and my eye was caught by the Conservative Henry Smith's debate on government policy on animal experiments.
In the Lords (from 2.30pm) questions include one from Labour hard man Lord Campbell-Savours, about reviewing the arrangements for enforcement and monitoring of the ministerial code - watch out for a supplementary, perhaps directed at some of the ex-ministers who've served in the Coaltion for a short while, and then moved on.....
Another Labour peer, Lord Dubs, picks up a theme pursued by colleagues in the Commons with a question on official visits to food banks made by ministers of both Houses since May 2010.
Then there's some important legislating. First up is the report stage of the Scrap Metal Dealers Bill. There's a bit of backstory to this. At committee stage, peers voted down an amendment the government had promised to defuse opposition to the bill in the Commons - to add a "sunset clause" - leaving the MPs that accepted assurances that it would be added rather peeved. Will the government try again, if only to be seen to be trying to keep its promises?
Then it's on to the report stage of the Defamation Bill - after long days of detailed scrutiny in Grand Committee. All sides believe that the result of the discussion so far has been to produce a much better public interest defence against libel actions, that something was published responsibly in the public interest.
But other issues remain...what should the obligations of website operators be, if someone posts defamatory comment (accusing someone of child abuse, for example) on some busy site? A lot of peers believe there is scope to toughen up the requirements for operators to monitor who posts on their sites and address complaints - and the Liberal Democrat Lord Phillips of Sudbury has an amendment on this issue, giving website operators various defences, including rapid response to a complaint.
There will also be important Opposition amendments to restrict the rights of corporate organisations to sue for defamation and seeking to extend the current restrictions on local councils suing for defamation (recent events at Rutland County Council were raised at committee stage) and also to extend them to any private company providing public services.
And watch out for a series of amendments tabled jointly by the formidable alliance of Lords Puttnam and Mackay, and Baronesses Scotland and Boothroyd to create a "Leveson-esque" voluntary Arbitration Service for defamation cases.
There will also be a Motion to Regret the new NHS Bodies and Local Authorities (Partnership Arrangements, Care Trusts, Public Health and Local Healthwatch) Regulations 2012 - Lord Collins of Highbury will seek to highlight delays in establishing Local HealthWatch organisations.
On Wednesday, he Commons convenes at 11.30am for questions to the ministers at the government's administrative "engine-room", the Cabinet Office, and that's followed at noon by PMQs. David Cameron might like to stay in his place afterwards, to watch one of his backbenchers, John Baron, move a ten minute rule bill, which would legislate in this Parliament for a referendum on British EU membership after the next election.
Mr Baron gathered 100 signatures from Tory backbenchers for a letter to the prime minister suggesting this ploy, which he thinks would flush out the other parties on the referendum issue, and reassure an electorate which has become cynical about promised referendums. Now he wants to test the view of the House, and see whether the government supports or opposes him. Again, if this comes to a vote, the lists will come under intense scrutiny.
The day's main debate is led by the Democratic Unionist Party, on the subject of suicide prevention in the UK. While over in Westminster Hall (from 9.30am) there are more backbench debates - watch out for the 11am debate on tax transparency in FTSE 100 companies - led by the Conservative Stephen McPartland.
In the Lords (from 3pm) questions to ministers cover childhood obesity, reducing sugar consumption and whether the government intends to make any reforms of the composition of the House of Lords. Then peers take a detailed look at another private members' bill to have emerged from the Commons, the Prisons (Property) Bill , before turning to their fifth committee-stage day on the Growth and Infrastructure Bill. Key issues for this session include employee ownership and the controversial idea of allowing employment rights to be traded-off for shares.
On Thursday in the Commons, bleary-eyed MPs gather at 9.30am for business, innovation and skills questions, followed by the weekly statement on forthcoming Commons business - and then MPs move on to two debates on subjects chosen by the Backbench Business Committee. First: subsidies for new nuclear power - a good Coalition faultline subject, raised by MPs Martin Horwood, Caroline Lucas, and Mike Weatherley; then on the closure of A&E departments - an increasingly toxic local issue for many MPs including Virenda Sharma, Patrick Mercer, and Stephen Lloyd.
Across in Westminster Hall there are debates on two recent select committee reports - Environmental Audit Committee on Protecting the Arctic and the Defence Select Committee report on Future of Maritime Surveillance.
These are both, doubtless, worthy subjects, but these Thursday afternoon debates are regularly falling victim to galloping apathy, and collapsing early. Perhaps MPs are not willing to hang around on a Thursday afternoon for a Westminster Hall debate - but if these occasions are just going to be a chance for committee members to make speeches at each other, are they worth having?
In the Lords (from 11am), questions cover regulation of the civil and military use of drones, improving social housing stock and ensuring young people have a proper understanding of managing personal finances before leaving school. But the really fun part of the day is the motion from the former Liberal leader, Lord (David) Steel.
This looks like a continuation of his long guerrilla campaign to bring in a modest reform of the membership of the Upper House. On more occasions than even he cares to remember, Lord Steel has proposed a bill which would allow peers to retire, to be expelled from the House if convicted of serious criminal offences, and to exclude the 92 hereditary peers who continue to sit in it... that last provision was pulled in the face of a determined rearguard action, the last time the bill went through.
Lord Steel's bill languishes in the Commons, with no real prospect of being debated, let alone passed. And he is pretty miffed about that. So now he is proposing a motion that "Notwithstanding the practice of the House, this House resolves that no introductions of new Peers shall take place until the recommendations in paragraphs 36, 47, 57, 63, and 67 of the First Report of the Leader's Group on Members Leaving the House, have been implemented".
Essentially those recommendations call for a new deal to reduce the size of the House, offering pensions to peers who retire from it, and allowing the possibility of a vote by peers on which of their numbers should be culled, and an understanding that life peerage should not mean automatic membership of the House, without a significant commitment to service in it (ie turning up...)
With the prospect of 50 new peers being created, there are increasing worries that the membership of the Lords has risen at an unprecedented rate. Labour are circulating figures suggesting that since the general election, David Cameron has appointed 128 new peers - 43 a year, compared to the 18 a year created by Margaret Thatcher. Lord Steel may well be able to tap into that concern...
Peers will also canter through all the stages of the HGV Road User Levy Bill and debate the role of civil society in promoting peace in Israel and Palestine.
Neither House will be sitting next Friday.