Assessing the Democrats’ impeachment drive depends on answers to three crucial questions:

1) What did President Trump really want from Ukraine?

2) Can Democrats prove he wanted something so improper, so lawless that it meets the high bar for "high crimes and misdemeanors," bribery, or treason?

3) What’s the rush? Do voters think the charges are so serious, the proof so convincing, and the need to remove the president so urgent that it cannot wait until the election next November?

Question 1: What did the president want from Ukraine?

The Democrats argue — and have presented testimony — that Trump cared a lot more about getting Ukraine to investigate the Biden family than he did about advancing American national security. If Trump’s real goal was bringing down the Bidens, and if he tried to get Kyiv to do that by leveraging U.S. foreign aid and the prospect of a White House meeting, then he would be wrongly seeking personal, political benefits from a foreign government against a likely 2020 competitor.

Those are reasonable arguments. Indeed, they are the most likely explanations for the 55-day hold on aid to Ukraine, which Congress had authorized. Still, other explanations are possible, and the White House and its Republican allies have offered them. They say Trump had perfectly legitimate national-security concerns about U.S. policy in Ukraine, that he had often mentioned them to advisers, and that he paused the aid as he evaluated them.

After all, they say, Ukraine’s government was routinely ranked among the world’s most corrupt. Given that dismal record, wasn’t it prudent to wait, at least briefly, and see whether country’s new president lived up to his anti-corruption promises or sunk into the same sewer as his predecessors? After all, America frequently tries to promote good governance among its allies and has a direct interest in seeing its aid dollars spent honestly, not siphoned off to corrupt oligarchs and their political friends.

If the new president, Volodymyr Zelensky, really intended to root out corruption, wouldn’t he gladly say so publicly? Wasn’t that especially true of corruption in the notorious energy sector? What’s wrong with asking for Zelensky to say publicly that he intended to investigate that? In any event, the aid was released without that promise and Trump did meet with Zelensky. No harm, no foul. (Not good enough, Democrats say. It is simply wrong for the president to ask a foreign government to investigate a U.S. citizen. When the target is a domestic political opponent, the request is doubly wrong, even if nothing comes of it.)

Beyond the corruption issue, Trump had a second, legitimate policy concern. He has long been skeptical of foreign aid. He said it often during the 2016 campaign and has incorporated it into his broad reorientation of American policy. He was elected, in part, because voters endorsed those views, according to polls. Trump’s allies note that he has held up aid to other countries and asserted those policy concerns about Ukraine in White House meetings. Ambassador Kurt Volker underscored those points in his testimony.

If foreign-policy experts at the Departments of State or Defense or the National Security Council had different views, so be it. A wise president would listen to them — and then make his own choice. But only the president was elected, his backers stress, and policy differences should never be grounds for impeachment.

Question 2: Can the Democrats prove their case? Can they show conclusively that the president wanted something illicit and was using official resources to get it?

The Democrats’ problem here is that Trump has a plausible alternative explanation for temporarily holding up the Ukrainian aid. That explanation may be less persuasive than the Democrats’ assertion of self-interest, but that’s a matter of opinion. The Republican explanation is not fanciful, and there is some evidence to support it. Besides the concerns about corruption, the White House wanted to know if Ukraine had illegally meddled in the 2016 U.S. campaign, supporting Hillary Clinton and opposing Donald Trump.

To demolish these Republican arguments and prove their own, Democrats need to offer firsthand proof. That’s the only way to prove what Trump’s motives really were. They need documents or testimony from people who dealt directly with the president. Rumors, conjectures, and presumptions are simply not enough.

The only firsthand accounts so far are those of Gordon Sondland, U.S. ambassador to the European Union, and one of his aides, who overheard part of one call. Trump spoke directly with Sondland and said he wanted nothing from Ukraine and had no “quid pro quo” for resuming the aid disbursements. Trump's call, which came after news of congressional investigations broke, sounds rehearsed and self-serving. Still, it is the only firsthand testimony about Trump’s motives we have so far, aside from the transcripts of two calls between Trump and Zelensky.

If Trump spoke with other advisers about this issue, House Intelligence Committee Chairman Adam Schiff is not willing to wait for their testimony. Schiff subpoenaed several of them. When Trump told them not to come, the advisers then asked the federal courts to rule on the issue. Schiff and his fellow Democrats say this normal exercise of due process rights constitutes “an obstruction of Congress.” It’s a novel idea. Nobody had heard of this “crime” before. Quite the contrary. It is common for courts to adjudicate a conflict between the executive and legislative branches. Still, Schiff has repeated his charge frequently and seems determined to include it as an article of impeachment.

The bottom line is what Scottish courts call “unproven.” Crimes that carry draconian punishment rightly require conclusive evidence to match. So far, the Democrats have not produced it. To unmask Trump’s malign intentions, Schiff and his committee need documents from the president himself or testimony from those who spoke directly with him. They simply don’t have them, and they aren’t willing to wait. Meanwhile, Trump and his allies have offered a plausible alternative account, if not an entirely convincing one. The Democrats have no way to demolish it without firsthand accounts.

Question 3: What’s the rush?

So much attention has been devoted to Trump’s motives and the contested evidence for them that very little has been paid to how grave the alleged crime is (assuming it can be proven) and why the president needs to be removed immediately.

“Gravity” and “urgency” are closely related here. The graver the offense, the greater the need to remove the president quickly. It’s up to the Democrats to make that case. As yet, they’ve hardly tried.

Speaker Nancy Pelosi, Adam Schiff, and progressive members of the Democratic caucus have certainly shown that they are in a hurry. What they haven’t shown is why independent voters and centrist Democrats should be, too.

Two key pieces of evidence indicate the public is prepared to wait until November 2020 and decide for themselves whether Trump is fit for office. The first is polling. Trump’s overall popularity has remained remarkably steady in national polls. It’s in the low- to mid-40% range and edging up. In battleground states, it is slightly better. What must trouble Democrats is not only the battleground numbers but the trend, which favors the president, not Pelosi. The second clue is that Democratic presidential candidates are not emphasizing impeachment or the urgent need for it. They offer the usual formulaic answers when MSNBC debate moderators ask about it, but the candidates themselves don’t bring up the topic. They must be looking at internal polls and focus groups that show even partisan audiences in Iowa, New Hampshire, and South Carolina have other, more pressing concerns.

The voters are saying, “Where’s the fire?” Schiff and Pelosi must be wondering the same thing and asking, “Where do we go now?” Unfortunately, they have already pulled the fire alarm. It’s the second time they’ve done it, and the first responders are getting grumpy.