As Senate Republicans wait on tenterhooks for Vice President Mike Pence to talk trade with Mexico's foreign minister, a new Quinnipiac poll should have the entire party shaking in its boots right now.

Sen. John Cornyn, R-Texas, who's up for reelection, can feel pretty secure in his incumbency. His net approval rating is in the double digits, and Beto O'Rourke, favored by Texas Democrats to abandon his doomed presidential bid in favor of challenging the Senate seat, seems unlikely to jump ship.

Trump's net approval rating is one point underwater. If he runs against Sen. Bernie Sanders, I-Vt., or Sen. Kamala Harris, D-Calif., he'll likely be OK.

But Quinnipiac found that former Vice President Joe Biden would beat Trump — in Texas — 48% to 44%. This is greater than the margin of error for the poll.

Super Tuesday is still eight months away, and Biden hasn't even begun to fall under the barrage of attacks the Left is preparing for him. If the Trump economy keeps humming along as it has been, it's fully possibly that even if Biden does win the primary, he'll be battered enough that Texans decide not to change horses mid-race.

But I would feel a lot more confident in Trump's odds if he weren't threatening a trade war expansion that would cripple Texas' relationship with Mexico, its largest export market.

If Trump does go through with his initial 5% tariff threat against Mexico, Texas would likely lose 117,335 jobs, $7.1 billion in income, and nearly $11.9 in gross state product. If he decides to escalate tariffs to the 25% level, the state would pay tens of billions of dollars in border taxes.

Bringing a trade war to Mexico wouldn't just cost Texans dollars and jobs; it could blow up trade talks to agree to the long-term USMCA deal entirely. If Mexico takes its cue from Trump's never-ending trade war with China, they may pull out of the deal, which is languishing in the Democratic-controlled House.

If Trump's running 4 points below Biden in Texas while the economy is still this hot, how much more could he lose by if he torpedoed the state's economy? Would it be enough to blow Cornyn's lead and hand Democrats yet a free Senate seat?

Trump's dreams of a global trade war may not just be terrible economics but potentially disastrous political strategy. The Republicans threatening to override his tariff veto may be saving not just themselves but Trump's entire presidency.