Dean Obeidallah, a former attorney, is the host of SiriusXM radio's daily program "The Dean Obeidallah Show" and a columnist for The Daily Beast. Follow him @DeanObeidallah . The opinions expressed in this commentary are his own. View more opinion articles on CNN.

(CNN) Call me old fashioned, but I thought the Democratic speaker of the House was supposed to bolster House Democrats and hold a Republican President accountable. As of late we are seeing just the opposite from Speaker Nancy Pelosi.

The latest example came Sunday when the New York Times' Maureen Dowd reported that Pelosi had slammed four of the most vocal and visible freshman House members, Reps. Alexandria Ocasio-Cortez of New York, Ilhan Omar of Minnesota, Rashida Tlaib of Michigan and Ayanna Pressley of Massachusetts.

Pelosi's criticism came after a June 25 vote in which the four were the only Democrats to oppose a House bill to provide funding for the crisis at the southern border because as they put it in a statement , "in good conscience, we cannot support this supplemental funding bill, which gives even more money to ICE and CBP and continues to support a fundamentally cruel and broken immigration system."

In response to that vote, Pelosi told Dowd, "All these people have their public whatever and their Twitter world," adding, "But they didn't have any following. They're four people and that's how many votes they got."

In response, Rep. Ocasio-Cortez took to Twitter, focusing in on the dismissiveness of the speaker's "public whatever" remark. "That public 'whatever' is called public sentiment. And wielding the power to shift it is how we actually achieve meaningful change in this country," she tweeted.

What makes Pelosi's remark so stunning is that it flies in the face of her often-repeated philosophy that she has espoused to House Democrats since taking control of the chamber in the 2018 midterms. "Our diversity is our strength and our unity is our power," she wrote last November.

Pelosi is 100% correct with that approach. That means, though, that diversity of opinion needs to be respected -- not belittled. This unity is vitally needed in the time of Donald Trump, since the Democrat-controlled House is the only chamber that serves as a legitimate check on the President.

This brings us to the second issue with Pelosi's leadership: her refusal to hold Trump accountable using all the tools she has as Speaker.

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Sure, Pelosi has been on board with traditional oversight of Trump by House committees.

But we have seen Trump and his regime stonewall many of these committees' requests. That was the case with the House Ways and Means Committee's demand for Trump's tax returns, requiring the committee to recently file a federal lawsuit to compel production.

In the meantime, Pelosi has prevented House Democrats from opening an impeachment inquiry to truly hold Trump accountable for his possible wrongdoing, as outlined in Robert Mueller's report. As CNN has reported , currently at least 80 House Democrats and one now former Republican support this approach. And beyond that, a recent Gallup poll found 81% of Democrats support impeachment proceedings against Trump. (You can't get 81% of Democrats to agree on anything!)

Beyond just Democrats, that same Gallup poll found that more Americans support impeachment of Trump now -- 45% -- than the number of Americans -- 19% to 38% -- who supported the impeachment of Richard Nixon at the beginning of the Watergate investigation. It's likely, given that Mueller identified 10 possible episodes of obstruction of justice by Trump, that support for impeaching Trump could rise if credible evidence were presented to make the case Trump did in fact commit a crime or crimes.

And it appears that Pelosi's refusal to allow impeachment proceedings to go forward is now helping Trump politically. A new Washington Post-ABC News poll released Sunday found Trump with his highest approval numbers yet as President, with 47% of registered voters approving of the job he's doing and 50% disapproving. In contrast , that same poll on April 25 -- a week after the Mueller report was released -- found that only 42% of registered voters approved of the job Trump was doing, while 54% disapproved.

Some might argue Trump's number went up five points because of a strong economy, yet the unemployment rate in April was 3.6% -- 0.1% lower than when this new poll was conducted. The one big difference between April and now is that the cloud of the Mueller investigation appears to have been lifted, in part because of Speaker Pelosi's refusal to begin impeachment hearings.

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Pelosi can easily rectify both of these issues, if she truly wants to. She can return to keeping fights within the Democratic House caucus behind closed doors to foster unity.

And given that Mueller is scheduled to testify before the House on July 17, that could mark the perfect time for her to launch an impeachment inquiry. The ball is squarely in Pelosi's court. Her decision on both issues will likely have a big impact on whether Trump wins re-election or a Democrat wins the White House in 2020.

Correction: An earlier version incorrectly described the bill opposed by four prominent Democratic House freshmen as a Senate-authored bill.