Rep. John Kline (R-Minn.) isn't ruling out a run against Sen. Al Franken (D-Minn.), he told reporters in the state on Monday.

Kline said he'd make a decision by the summer, the hardest evidence yet that he's seriously considering a bid. Rep. Erik Paulsen (R-Minn.) has also pointedly not ruled out a run.

The two are considered the GOP's best options to challenge Franken, who narrowly won his first election in 2008 but has worked hard since to improve his standing with voters and looks formidable heading into 2014.