To accomplish every major goal that Democrats have — fighting climate change, reducing economic inequality, improving health care and so on — the party must win the Senate. Doing so in 2020 would require winning a net of three Senate seats as well as the White House (because the vice president can break a tie). One Democrat, Doug Jones in Alabama, is likely to be an underdog next year, and his defeat would mean the party has to win four seats elsewhere. The party’s best opportunities are in Arizona, Colorado, Georgia, Iowa, Kansas, Maine, Montana, North Carolina and Texas, although most of those states lean Republican.

It may be too late for O’Rourke to run for Senate. Another impressive Democrat, M.J. Hegar, has already announced that she is running against Cornyn. But I think Democratic voters in Texas are right to be putting such a high priority on the Senate. Winning the White House isn’t enough for the party to make the changes its presidential candidates are promising.

“Even if Democrats manage to retake the White House, a Senate majority stands between them and the ability to pursue any real legislative agenda and, crucially, the ability to confirm nominees to the Supreme Court and other important positions,” Vox’s Tara Golshan and Ella Nilsen wrote this week, summarizing the Senate races. “Without the Senate, Democrats’ ideas will remain pipe dreams.”