Obama will hold events in the key electoral state of Pennsylvania, a must-win for him in 2012, and in vital swing state Florida, as an amended version of his $447 billion package faces a symbolic Senate vote.

The day will likely evolve into a new round of partisan posturing, as Republicans and Democrats, eyeing a date with voters next year, seek political advantage from a measure that has almost no chance of passing in full.

A populist Obama has vowed to fight relentlessly for the plan, a mix of tax cuts and infrastructure spending, and plans to castigate Republicans for doing nothing to tackle the jobs crisis if it founders in a gridlocked Congress.

"The more people know about the American Jobs Act; the more they hear the President talking about it; the more they want Congress to pass the plan," Obama's political confidant David Axelrod said in new campaign memo.

"The American people agree with economists across the political spectrum who are saying that the (act) will immediately create jobs and put more money in the pockets of middle class Americans who are struggling to make ends meet.

"Yet Republican leaders -- from Congress to the presidential campaign trail -- have been steadfast in their opposition without providing an alternative that would create jobs now."

Republicans, however, argue that even some lawmakers from Obama's own Democratic Party are wary of voting for the legislation.

Leaders in the Republican-led House of Representatives have told the president they will only agree, at most, to pass parts of the bill.

Democratic Senate Majority leader Harry Reid meanwhile is expected to call a procedural vote on an adjusted version of Obama's bill on Tuesday.

The measure swaps Obama's plan to pay for the legislation by curbing tax deductions for people earning $200,000 and families earning $250,000 a year with a 5.6 percent surcharge on those earning one million dollars and more.

Some Democrats, especially senators with tough 2012 races, have balked at Obama's approach as Republicans have charged them with waging class warfare and of backing a move that could hurt job-creating small business owners.

But they may be more likely to vote for Reid's version, which is billed as a bid to make the very richest Americans shoulder more of a burden for igniting an economic rebound.

Whatever happens, the bill is unlikely to advance since Democrats lack the 60-seat super majority needed to thwart Republican blocking tactics in the Senate.

But both sides will be keenly tallying the level of Democratic support for the bill, and an increasingly embattled president.

Obama, who has crisscrossed the country for the last few weeks demanding Congress "pass this bill" argues his plan will boost growth by two percent and shave one percent off the unemployment rate, currently at 9.1 percent.

Democratic strategists hope that if the plan fails to pass Congress in recognizable form, Republicans -- who brand it the latest in a series of failed stimulus measures -- will pay a political price with voters.