Did Wisconsin Rep. Paul Ryan’s budget put his Republican colleagues in a tough spot for reelection in 2012? Photographer: Joshua Roberts/Bloomberg

The final vote — 235 yeas, 193 nays — included only four Republicans casting “no” votes and not a single Democrat voting for the plan.

While the vote was quickly hailed as a victory by Republican leaders, there is reason to believe that for some of the 61 GOP Members who sit in districts President Obama carried in 2008 it may well be a defining moment — and not in a good way -- of their first two years in Congress.

The problem for targeted Republicans who are now on the record as in support of this bill is three-fold.

First, Ryan’s proposal to turn Medicare into a voucher system is politically treacherous. In a recent Gallup poll, just 13 percent of people favored a complete overhaul of Medicare. Just 18 percent said they supported major changes in the program.

That goes double for older (65+) people, who tend to be some of the most reliable voters in any election and went for Republicans by 21 points in the 2010 election

Any time a politician find himself on the opposite end of considerable public opinion on a given issue, it’s a dangerous place to be.

Or as former Fix boss Charlie Cook wrote in a recent column about Ryan’s Medicare proposal: “House Republicans are not just pushing the envelop — they are soaking it with lighter fluid and waving a match at it.”

Second, Democrats did their Republican counterparts no favors in the vote. House Minority Leader Nancy Pelosi (Calif.) succeeded in keeping Democrats unanimously opposed to the budget, ensuring that when election season rolls around Republicans will own their budget vote fully.

It’s a tried and true strategy and one that was successfully employed by Senate Republicans on President Obama’s economic stimulus bill — only three Republicans voted for the plan — and the health care law that garnered zero GOP votes.

The lack of GOP involvement in those two pieces of legislation allowed Republicans to run — and run hard — against both proposals in the 2010 election.

Reverse the party names and substitute “budget” for “health care” and you get some sense of what some GOP incumbents might be headed for next fall.

Third, the vote may ultimately be pointless legislatively since Senate Democrats aren’t likely — to say the least — to pass the Ryan budget any time soon.

The apt comparison could well be the June 2009 cap and trade House vote. The energy bill — it was officially known as American Clean Energy and Security Act — passed the House narrowly but ran into a blockade in the Senate which was never resolved.

That left lots of House Democrats — including a large number representing districts in the industrial midwest — having to answer for a vote that was broadly unpopular in their region and for which they had no successful final product.

House Republicans will try to avoid that fate by casting the vote as a necessary first step toward deficit reduction — something that all Americans believe we need.

And, it might work. But, history is littered with politicians who took a principled vote — Marjorie Margolies-Mezvinsky is a prime example — and ultimately lost because they were unable to defend it in the back and forth of a political campaign.

To avoid that fate targeted Republicans need to begin their defense of today’s vote now — and not stop until all of the ballots are cast in November 2012.