Hillary Clinton is preparing for two different foes in Monday’s presidential debate: an on-message, disciplined Donald Trump and a freewheeling, more provocative Donald Trump.

The Democratic nominee has cleared her schedule on multiple days to test arguments and practice for her first 90-minute matchup with the GOP nominee. This week, she has convened a small group of top advisers to run through potential questions and help her anticipate an assortment of scenarios.

In contrast, Mr. Trump has played down the value of doing dry runs and warned of the perils of over-preparation.

In mock debates and closed-door sessions that last hours, Mrs. Clinton and her top advisers are prepping ways to use Mr. Trump’s own words against him. Campaign officials say Mrs. Clinton also must make a positive case for her candidacy while reminding voters of her rival’s most controversial comments.

The Clinton campaign has employed a similar strategy during the past few months in ads and speeches highlighting Mr. Trump’s own statements.