Sen. Claire McCaskill raised more than $1 million for her 2012 re-election campaign during the first quarter, the Associated Press reported Tuesday. The first-term Missouri Democrat dwarfed the fundraising effort of one potential Republican opponent, Ed Martin, who announced earlier in the day that he had raised more than $162,000 in the same period.

McCaskill raised $1.05 million and had nearly $1.8 million cash on hand, according to her campaign.

Martin, who unsuccessfully ran for the House in 2010, was upbeat in an email to supporters Tuesday. “At the end of the first quarter of 2011, our campaign has taken in over $162,000 — this despite beginning the race partway through the quarter! Again, I cannot tell you how encouraging this is,” he wrote.

Martin is running in the GOP primary with former state Treasurer Sarah Steelman, but he is widely viewed as the underdog in the Republican race. Steelman had not released her fundraising report by Tuesday evening.

McCaskill is widely considered among the most vulnerable Senate Democrats. She has recently been snared by revelations that she expensed taxpayers for chartered flights she took aboard a plane she partly owned, and her troubles continued days later when it was revealed she owed more than $300,000 in unpaid property taxes.

Shira Toeplitz contributed to this report.