Several things have occurred in the last 2 months.

First, Iran has multiple times launched attacks on U.S. and other oil tankers in the Persian Gulf, mining ships, seizing vessels, and most recently a missile attack that was alleged to be from Yemen, but was traced back to Iran. Iran is desperately trying to start a war with the United States, and Democrats are giving Trump no credit for skillfully avoiding a war, and instead just continuing to tighten sanctions that are bringing Iran to the edge of collapse.

I don't think we've ever had a president who has more effectively used sanctions, with North Korea, with Iran, with Russia, with China, with Mexico, using our economic power to bring an enemy nation into submission, instead of a war. Instead of a costly war, it strenthens us while crippling them.

Trump was given no credit for avoiding a war when Iran was attacking ships with mines, and then shot down one of our unmanned military drones, resisting those within his security council who were pushing Trump to war. Against the wishes of his advissors, he averted a war, literally calling back the attack that would have killed about 150 Iranians. Trump called the potential attack too much, and "disproportionate".

And about a week ago, Trump fired (or accepted the resignation of, depending on which side you listen to) John Bolton. Which I think many agree lessens even more the chances of war.

In Afghanistan, Trump is attempting to end the war in Afghanistan, and was at least willing to have negotiations with the Taliban, until the Taliban launched an attack during the negotiation period and made it clear they were unserious about peace, and completely untrustworthy. But regardless, Trump is unconcerned with what is traditionally proper or acceptable, and is willing to explore all options before going to war.
And no one running for the presidency, Democrat or Republican, in 2016 or now, would have made the innovative choices that Trump has, and avoided war, and at least met with Kim Jong Un, and offered meetings with the Ayatollah and with the Taliban, opening the door for negotiation and planting the seeds for later peace.

The Demcorats (and the establishment/never-Trump/Deep State Republicans) desperately want Trump to start a war that would hurt him in the polls, the only thing at this point that would obstruct Trump from getting re-elected in 2020, other than a failing economy.
If Trump were going to start a war, he would be well advised to wait until after he is re-elected. But really, I think the obstruction to a peace deal, with Kim Jong Un, with China, with Iran, with the Taliban, is that they think they can hold out in the hope Trump will not be re-elected. But as soon as Trump is re-elected and they know they have to continue dealing with Trump, and with Trump's sanctionss, they will negotiate a trade deal.
But the Democrats and our enemies worldwide have a shared goal of crippling Trump politically, and removing Trump from office, so they can go back to the shared business of selling out and destroying America.