Last month, Joe Biden thought China was "not competition for us." This month? "You bet I'm worried about China."

So goes the most recent flip-flop—er, evolution—by the Democratic frontrunner. We do not know what has happened with China to make Biden change his tone from May 1, when he said, according to Axios:

"China is going to eat our lunch? Come on, man — They can't even figure out how to deal with the fact that they have this great division between the China Sea and the mountains in the West. They can't figure out how they're going to deal with the corruption that exists within the system. They're not bad folks, folks … They're not competition for us."

Tuesday in Iowa, Biden had a completely different opinion. Now, China is a serious threat—and it's President Donald Trump's fault.

We are in a competition with China. We need to get tough with China. They are a serious challenge to us, and in some areas a real threat. And every single step that Donald Trump is taking is only exacerbating the challenge. While Trump is tweeting, China is making massive investments in technologies of the future. While Trump is name-calling, China is building roads, bridges, and high-speed rail. While Trump is pursuing a damaging and erratic trade war, without any real strategy, China is positioning itself to lead the world in renewable energy. While Trump is attacking our friends, China is pressing its advantage all over the world. So you bet I'm worried about China — if we keep following Trump's path.

So far, Biden has kept his campaign focused on President Trump rather than his primary opponents. He has a sizable lead in the primary polls right now, but if he continues blatantly flip-flopping like he's done on this issue and on the abortion-related Hyde Amendment, he might not have a need for speeches that mention the president more than 70 times.