Since President Trump is unpopular, Democrats have a clear political incentive to tar the Republican Congress with Trump's unpopularity. But this is not simply a political gambit. They make his actions possible. They are responsible for virtually everything he's doing.
How unpopular is he? The latest reputable poll (Quinnipiac) puts Trump's approval rating at 36%, an unheard of level of unpopularity for a new President. Gallup's number has generally been more favorable to Trump. But according to numbers released today, his net approval rating dropped 8 points during his first week in office. Again, virtually unheard of.
Meanwhile a new AP-NORC poll shows weak for repealing Obamacare and that 56% of American are either "extremely" or "very" worried that many Americans will lose their health care coverage if Obamacare is repealed. An additional 27% are "somewhat" concerned.
The President is unpopular. His main policies are unpopular. His behavior is unpopular. The Congress makes everything he's doing possible. Most of them are up for reelection in less than two years.