Rep. Sean Duffy, R-Wis., unloaded on his state's Democratic senator during a conference call with reporters on Wednesday.

As he pitched his party's tax reform efforts, the Wisconsin congressman zeroed in on Sen. Tammy Baldwin's record of supporting liberal policies. Baldwin, Duffy said, "has voted in favor of higher taxes and fees 407 times."

The senator is one of ten members of the upper chamber running for re-election in a state won by President Trump in 2016, putting her in a tough position as the midterms approach. Among those senators, Duffy said, Baldwin has the "unique distinction" of being the only one in favor of the single-payer healthcare plan introduced by Sen. Bernie Sanders, I-Vt. last month.

More broadly, Duffy argued Baldwin believes "the federal government, the bureaucrats in this town, can spend your money better than you can."

Duffy, whose rural Wisconsin district voted for Trump by more than 20 points, is optimistic congressional Republicans will be able to build a coalition big enough to pass tax reform this year. The Senate's failure to pass healthcare legislation has created a "sense of urgency" among upper chamber Republicans, according to Duffy, who also lauded GOP leadership for bringing members of the House and Senate together to work on a framework for tax reform legislation. That move puts Republicans "light-years ahead" of the healthcare reform process, he contended.

In February, Duffy announced he would not be running in the Republican primary to challenge Baldwin for her seat next fall. But by late September, National Journal reported he was "reconsidering" a bid for the seat and had raised $550,000 in the third quarter. "Congressman Duffy has support from all over Wisconsin, and he's well prepared for whatever is on the horizon," his spokesman Mark Bednar said at the time.

Emily Jashinsky is a commentary writer for the Washington Examiner.