Upon reflection, did the populist party make a wise decision in choosing to support the democratic party’s candidate in the 1896 presidential election? why or why not?

No, the Populists did not make a wise decision by supporting the Democratic Party because the Populists aligned with a very similar party. During that period, there was a growing two-party system in American politics and this eventually helped to end the Populist party because they lost their autonomy to the Democratic party. They were even called “democrats in sheep’s clothing”.

Yes--third parties don't work in our electoral college system. They would not have gotten any of their goals without a major party. 

Though the Populists joining with the Democrats still don't get them a win in 1896, their ideas become more mainstream. With a big party owning their ideas on the Democratic Platform, they will get more traction. Many of the Populist ideas like an income tax and direct election of senators will happen during the Progressive Era becoming the 16th and 17th amendments.

it proved indian land claims were unjustified.