Can Churches Discuss Politics?
The short answer is: Yes!
A 501(c)(3) may not support a specific candidate, but may engage in politics, so long as it is not a "substantial portion" of its activities.
According to the Council of Non-Profits, a church or other 501(c)(3) may not "participate in, or intervene in (including the publishing or distributing of statements) any political campaign on behalf of (or in opposition to) any candidate for public office.” (emphasis added)
The Council says, "Engaging in lobbying by charitable nonprofits is permitted so long as the nonprofit does not expend more than an 'insubstantial' amount of energy, finances, or other resources towards the lobbying activities. Charitable nonprofits that engage in a 'substantial' amount of lobbying may be exposed to IRS penalties ('excise taxes')." (emphasis added).
The IRS says that a non-profit may "take positions on public policy issues," even issues that "that divide candidates," so long as care is taken not to support or oppose a specific candidate, such as "[a] message that shows a picture of a candidate ... or contains other distinctive features of a candidate’s platform."
The IRS also says, "A 501(c)(3) organization may engage in some lobbying, but too much lobbying activity risks loss of tax-exempt status."
In other words, talking to your congregation about the dangers of marijuana legalization, urging them to vote to overturn laws allowing recreational marijuana use, inviting someone from Dump the Skunk are all allowed!