The White House sent a letter to House Speaker Mike Johnson (R-La.) early Friday with a clear message: Your impeachment inquiry of President Biden is over.

Why it matters: The letter signals the White House's increasingly aggressive offense on impeachment, as Democrats see the GOP inquiry fizzling out.

• House Republicans have spent the last year and a half on an impeachment probe that appears unlikely to end in charges against President Biden.
• The investigation — launched amid Republicans' allegations that Biden improperly benefited from his son Hunter's foreign business dealings — hasn't proven any criminal wrongdoing by the president.
• The letter to Johnson from White House counsel Edward Siskel comes as a growing number of Republicans acknowledge that impeaching Biden is unlikely. Johnson himself hasn't committed to holding a vote on any impeachment articles.

The big picture: The GOP investigation was always an effort to undermine Biden's case for re-election. The probe has had many offshoots, focusing on the finances of the president's family, discredited allegations about a bribery scheme, and scrutiny of the Biden family's alleged influence peddling.

• The investigation, as Siskel points out, has included interviews with dozens of witnesses, including Biden's son and brother.
• "It is obviously time to move on, Mr. Speaker. This impeachment is over," Siskel wrote.
• "There is too much important work to be done for the American people to continue wasting time on this charade."

The White House believes that voters want Congress to focus on policy challenges such as funding the government and supporting Ukraine as it tries to fend off Russia's invasion.

Zoom in: Biden's administration began putting together a team to defend against an impeachment investigation as early as the summer of 2022, hiring lawyers and aides.

• That effort accelerated after former Speaker Kevin McCarthy (R-Calif.) unilaterally opened a probe last September and the House officially authorized the impeachment inquiry in December.

Driving the news: Siskel's letter comes three days after congressional testimony by former special counsel Robert Hur, who investigated Biden's mishandling of classified documents and decided not to prosecute.

• Siskel's letter describes the GOP lawmakers' interest in the documents case as "a flotation device for the sinking impeachment effort."
• Hur's testimony failed to unearth any bombshell revelations linked to the impeachment probe.

What they're saying: Johnson's team shot back at the White House letter, saying in a statement to Axios that it's "not surprising" the Biden administration wants the investigation to be over.

• "The White House does not get to decide how impeachment gets resolved, that is for Congress to decide," Raj Shah, deputy chief of staff for Johnson, wrote in a statement.