Note: American Presidential Elections Not Determined By Republican Primary Voters

Eeyores are going to Eeyore, and I’m sure Mark Halperin is developing theories about how committing one massive blunder after another is actually a winning approach as I type. But Donald Trump is a terrible candidate and he may be taking at least the Senate down with him:

The presidential race may have reached a turning point, as a new group of polls shows Hillary Clinton clobbering Donald Trump nationally and in swing states.

A new national Fox News poll shows Clinton beating Trump by 10 percentage points, 49 percent to 39 percent — Clinton’s strongest post-convention national performance yet.

In Pennsylvania, a state most observers believe is a must-win for Trump considering how the electoral math is shaping up, Franklin & Marshall has a new poll showing him trailing Clinton by 11 points — 49 percent to 38 percent.

In New Hampshire, another swing state that was believed to be relatively close, WBUR’s new poll gives Clinton a massive 15 point lead over Trump (47 percent to 32 percent).

And in Michigan — traditionally a Democratic state but one the Trump campaign had fantasized about winning as part of a “Rust Belt” strategy — Trump is down at a dismal 32 percent compared to Clinton’s 41 percent, according to Detroit News and WDIV-TV.

[…]

Worse yet for Republicans, Trump’s dreadful performance also looks to be imperiling their hopes to keep the Senate.

The new New Hampshire poll shows Sen. Kelly Ayotte (R) down by 10 points to her challenger, Gov. Maggie Hassan (D) — an awful result for an incumbent. And in Pennsylvania, Sen. Pat Toomey (R), who’s believed by political professionals to be a much stronger candidate than his challenger Katie McGinty (D) — is losing by 1 point as well.

As I wrote back in May, there is a Senate race in nearly every competitive presidential swing state and in some traditionally red states that could be surprisingly close this year (like Indiana, Missouri, and Arizona). So Democrats have long hoped that Trump’s presence at the top of the ticket could offer them a Senate landslide, and the party has generally done a solid job recruiting candidates for these races.

In the past few months, Republican Senate incumbents have generally remained slightly ahead in polls. But Ayotte and Toomey’s troubles — especially Ayotte’s, since she’s in a much worse position — show that this may not last.

Ayotte, ridiculous weasel-wording aside, endorsed Trump. Trump has returned the favor by refusing to endorse her. Republican Senate candidates now face the paradox that Trump is an anchor on their chances, but if the collapse in Ted Cruz’s polling numbers is any indication attacking Trump is a cure worse than the disease. A dilemma the Republican Party could not deserve more richly.

Admittedly, once Americans find out about Hillary Clinton’s all-quinoa diet, it will be Trump in a landslide.