Sen. Mark KirkMark KirkHigh stakes as Trump heads to Hill Five things to watch for at Trump-Senate GOP meeting Giffords, Scalise highlight party differences on guns MORE (R-Ill.) begins 2015 with a $2 million war chest, as he heads into what's likely to be a tough reelection fight.

The top-targeted GOP senator raised more than $600,000 from October through December 2014, according to Crain's Chicago Business.

That's a solid haul for a candidate not up for reelection during a fundraising quarter when others were scrambling for last-minute cash, though he (and his opponents) will have to raise much more than that each quarter to stay competitive.

Kirk's most likely opponent, Rep. Tammy DuckworthLadda (Tammy) Tammy DuckworthDemocrats scramble to contain Franken fallout  Overnight Regulation: Senate tax bill to include ObamaCare mandate repeal | Sessions sidesteps questions on WH influence on AT&T merger | Dems seek more transparency on student borrower rule Senate confirms ‘torture memo’ author to lead Transportation Dept legal office MORE (D-Ill.), heads into 2015 with more than $1 million in the bank after raising $460,000 over the same time period.