Want to pass a major infrastructure bill of at least $1 trillion (probably over 10/years), though truthfully we need more like $3-$4 trillion over 10 years.
Trump wants it passed without new taxes, the Dems will only
Infrastructure bills (designed and implemented well) will take about 8-12 months after being passed to start stimulating more economic growth (new jobs, etc.) and mostly help with long-term growth
New taxes would take effect immediately
So if Trump passes the infrastructure bill with Dems in a bi-partisan way, with new taxes involved
He's actually hurting the economy short-term, thereby hurting his chances in 2020
By the time Dems take the
This would make the Dems look like they managed to get something good done even with the likes
So Trump wants the infrastructure bill without new taxes because even though it'll still take 8-12 months to come into
This will help propel Trump to a 2020 victory.
Of course, there are also debates about how much to invest in which kinds of infrastructure--you have big oil battling big green energy (though not as much because big oil owns a good chunk of big green now), and much more.
Because if the economy is still growing at that point in time, they will want to stimulate it further and hope to keep the music
Trump can't afford to raise taxes, especially because if the economy continues growing, the Fed could start raising rates again even as the price of oil goes up