Is it fantasy politics to claim that Plaid could hold the balance of power after the general election?
Plaid's MP for Carmarthen East and Dinefwr Jonathan Edwards told me they came up with this message in 2010 but no-one believed them.
The question is whether people do now?
Things are very different in 2015 than they were in 2010. We've had five years of a coalition government, there's expected to be a tight general election and the polls are indicating that the SNP are going to be a real force.
Unlike in local and assembly elections, Plaid are vulnerable to the attack from their political rivals that a vote for Plaid at Westminster is a wasted vote.
That's why the push for plausibility, when they say they could hold the balance of power, is so important because it neutralises that criticism on the doorstep in places like Llanelli.
On other matters, Leanne Wood's speech was dominated by criticism of austerity.
The anti-austerity message is one of the big issues Plaid shares with the SNP, together with opposition to the nuclear deterrent, although Nicola Sturgeon has indicated that the SNP would support a future minority Labour government on a case by case basis even if it renewed Trident.
There's been lots of talk about the TV leaders' debates.
The prime minister's proposal fits in well for Plaid because it gives them a slot at the top table for the seven-way debate in which they can characterise themselves as the voice of Wales, and as an added bonus they won't be squeezed out of a head-to-head if David Cameron continues to refuse to take part.
There was also an eye-catching proposal to ring-fence a pot of money in the NHS to improve access to new drugs.
This has become a hugely controversial subject.
Plaid were keen to point out that this is not modelled on the Conservatives' cancer drugs fund, as it's available for medication dealing with all conditions.
The Welsh government says a focus on cancer, over and above other illnesses, is unethical.
The money comes from a rebate the pharmaceutical companies pay the UK government. The point is that this isn't cash that has come from thin air, it currently goes into general Welsh NHS coffers. Next year Plaid estimate that it'll be worth around £50m.
On the constitution, Leanne Wood continued with her criticism of the St David's Day agreement, which set out proposals to devolve further powers.
Privately, one source told me that on one level Plaid are delighted with the way that we now have a Labour first minister and a Conservative Welsh secretary trying to out-do each other on how far they go on devolution.
The tone of the debate has shifted in Plaid's direction.
I'm thinking here of David Jones now not being in government any more and Labour's Owen Smith saying you can't get a fag packet between him and Carwyn Jones when it comes to devolution.
There was also confirmation from Plaid that it now formally says there doesn't need to be a referendum on whether income tax should be devolved. This is the battleground in terms of future devolution.
In the context of all of the changes currently underway in the UK, Plaid believe it's ridiculous to hold one on something like the partial devolution of one tax.
The counter-argument is that we're talking about devolving the biggest tax of the lot, and making the assembly responsible for raising revenue worth £2bn.
There are also many others out there who don't believe the referendum is winnable. For Plaid, it's a process that doesn't even need to get off the ground in the first place.