Good Tuesday morning. Here are some of the stories making news in Washington and politics today.

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• When 20 Democratic presidential candidates gather for the second round of debates, about half of them will do so with the understanding that it will probably be their last time on the national stage this election cycle. Short of a breakout moment that charges fund-raising, many are in danger of missing the qualifying threshold for the next round of debates.

• Tonight’s debate will place the race’s two liberal front-runners, Senators Elizabeth Warren and Bernie Sanders, center stage. Here are more matchups to look out for.

• Joe Biden’s halting performance at the June debate has stirred unease among some Democrats about his age. They are looking for reassurance from his next debate on Wednesday.