Romney was attacking Obama's economic policies even as the president's standing in the polls has improved in recent weeks along with signs that the U.S. economy was on course for a sustained recovery.
But Obama, who is unopposed in the Democratic primary, remains vulnerable in the November election because of the financial turmoil that hit Americans as a result of the Great Recession and consumed most of his energies.
The most dramatic downturn in the U.S. economy since the Great Depression of the 1930s began as a result of the near financial meltdown in the final months of the George W. Bush administration.
Romney acknowledged that the economy was moving in the right direction as hundreds of thousands of jobs have been created, the unemployment rate has dropped and consumer confidence has jumped, but suggested that happened in spite of the president.
"The economy always comes back after a recession of course," Romney said Monday, previewing what could be a general election argument. "There's never been one that we didn't recover from. The problem is this one has been deeper than it needed to be and a slower recovery than it should have been."
Romney spoke on the eve of the Illinois primary, one of the premier battlegrounds in the drawn-out state-by-state contests for delegates to the national convention in late August in Tampa, Florida.
Republicans will vote next in Louisiana on Saturday before a break in the primary season that doesn't end until late June.
Romney and a growing number of Republicans across the country are eager to move beyond the increasingly nasty primary campaigns that have consumed far more energy, resources and political capital than most expected.
But the former Massachusetts governor has so far struggled to win over his party's most passionate voters — tea party activists and evangelicals who don't trust him as a true conservative.
Polls show Romney as favored in Illinois, but the race will be far closer than in Puerto Rico on Sunday where the former Massachusetts governor trounced Rick Santorum, his chief rival and a former Pennsylvania senator.
And even should Romney lose, Santorum will be unable to win all 54 Illinois delegates.
His campaign failed to file the proper paper work on behalf of 10 candidates for delegates who would be aligned with Santorum at the convention.
And even with a win, Santorum has almost no hope of overtaking Romney in the delegate tally. The nominee needs 1,144 to become the Republican standard-bearer against Obama in November. Romney has 521 delegates, Santorum 253, Newt Gingrich 136 and Ron Paul 50, according to The Associated Press count.
But Romney's inability to shake off a seemingly weak rival like Santorum highlights the struggles of his candidacy, an inability to generate excitement among the Republican voters. It also means Romney has to spend time and money fighting primary battles instead of turning his full attention to defeating Obama.
Santorum has all but conceded he cannot earn enough delegates to win, but claimed he was in the contest for the long haul because Romney is a weak front-runner.
With Republicans locked in their extended primary campaign, the Obama campaign reported Monday it raised $45 million for his re-election bid in February, bringing his total to about $300 million for this election cycle, his campaign said Monday.
Obama stepped up fundraising efforts during the month, collecting nearly twice as much as the $23 million per month average he raised during the final three months of 2011 and more than the $29.1 million he raised in January. The money was spread among Obama's campaign, the Democratic party and two campaign funds.The campaign reported it had about $75 million in the bank through the end of January.
Romney and Santorum, by comparison, raised $11.5 million and $9 million respectively in February. Romney and his allies are spending heavily in Illinois.
