Many are talking about a possible run for the presidency in 2020, and polls have shown that (even though he has not said he would run) he finishes well ahead of several candidates that have declared. He usually posts numbers that rival those of Kamala Harris or Elizabeth Warren (the two declared candidates that poll the best), and better than Klobuchar, Booker, Gillibrand, Castro, and others already in the race.
But would a presidential run be his best bet? Maybe not. There has also been talk of him running against John Cornyn for the Senate in 2020, and Cornyn may be vulnerable. Cornyn's job approval numbers tend to be lower than those of Cruz -- and a recent poll shows O'Rourke would start out nearly even with Cornyn (he had to come from far behind when he took on Cruz, and nearly won)>
The poll is one done by Public Policy Polling. They surveyed 743 registered voters in Texas on February 13th and 14th, and their poll had a margin of error of 3.6 points. The results are shown in the chart below.
Right now, O'Rourke would only trail Cornyn by 2 points (47% to 45%, with 8% unsure). That margin is within the poll's margin of error. Those are amazing numbers for a Democrat in Texas, and they show that O'Rourke would have a really good chance of unseating Cornyn.
That might be a better path for O'Rourke. The Democratic presidential nominating race is going to be a mess with. It already has 11 candidates, and that could swell by 6 to 10 more. It will be interesting to see what choice O'Rourke will make.