With the Senate in play and Democrats sensing gains in the House, White House aides say President Barack Obama will get more and more involved in down-ballot races as Election Day nears.

Until Thursday, Obama’s public campaign rallies have focused almost exclusively on making the case for Democratic presidential nominee Hillary Clinton and against her GOP opponent, Donald Trump. That changed, however, when the president flew to Florida and dove headlong into GOP incumbent Sen. Marco Rubio’s re-election fight.

The president cast Rubio as exclusively career-minded and harshly criticized the former GOP presidential candidate’s work ethic and intention to vote for Trump despite criticizing his party’s presidential nominee.

[Obama Tells Trump to ’Stop Whining,’ Campaign Harder]

“Unlike his opponent, he actually shows up to work,” Obama said of Democratic Rep. Patrick Murphy, Rubio’s opponent. Obama questioned how Rubio could vote for a person he once called a “dangerous con artist.”