Elon Musk, by far the biggest known midterm donor, is single-handedly keeping the Republican Party afloat in some of its most vital races.

Musk's team reached out to Republicans in late August to discuss a train wreck they all saw coming: Unless the GOP poured more money into Texas immediately, the state's Senate race could be lost in a matter of weeks.

Why it matters: That chat set in motion a massive rescue operation for Republican Ken Paxton funded substantially by Musk, who gave $158 million to the GOP in September alone.

Musk's rescue gave Paxton's sleepy campaign new life and showed why the world's richest person is the X factor in the push to prevent a midterm debacle for President Trump's party.

Zoom out: It also helped Republicans avoid a death-spiral scenario: that propping up Paxton in Texas would force them to drain badly needed resources from other Senate battlegrounds.

Instead, Musk's money allowed Republicans to flood Texas' expensive TV markets and free up cash to shore up unexpectedly…