Partisanship

It is expected that if the ACHA passes, it will do so with solely GOP votes, just as the ACA passed with just Dem votes. It wasn't always this way.

In late 1940 FDR had just won an unprecedented (and now unrepeatable) third term as President, with 55% of the popular vote and 85% of the Electoral vote. FDR proposed that the US should be the "Arsenal of Democracy," supplying the sole major country still in the fight (Great Britain and her Empire and Dominions) with the means to fight. He then proposed "Lend-Lease," to allow the increasingly destitute British to acquire weapons, ammunition, and materiel even without the means to pay.

The House voted on the bill in February:

                                      Aye               Nay
Democrats                    238                25
GOP                                24              135

The Senate voted in March:

Democrats                      49                 13
GOP                                10                 17

Apparently, back then, it was thought the representatives of the people, not the party leadership, should decide on important issues.