This just happened last night. Someone in my household used the upstairs toilet, and it clogged badly. When I got home last night I used the plunger for about an hour to try to clear the clog. I got it to the point where the water in the bowl drained, but very, very, slowly. This morning, the bowl flushed properly, but the water drained slowly, not as slowly as last night. It one of those high efficiency low flush toilets (I'm not sure what the correct terminology is). The other toilets in the house work fine, it's just the toilet in the main bathroom that is proving to be a problem. I figured that there must be something in the line that is causing the problem, something that isn't quite dislodged but is becoming dislodged with each flush. The amount of water entering the bowl seems to be about right, as does the force of the water entering the bowl. It's just that that vortex that usually forms as the water is swirling around doesn't form, and the water doesn't "flush" the way the other bowls in the house do. I don't believe that it's a problem that will require major repairs, if at all, but I will defer to the expertise of more knowledgeable people on this matter. Thanks for your help.

This just happened last night. Someone in my household used the upstairs toilet, and it clogged badly. When I got home last night I used the plunger for about an hour to try to clear the clog. I got it to the point where the water in the bowl drained, but very, very, slowly. This morning, the bowl flushed properly, but the water drained slowly, not as slowly as last night. It one of those high efficiency low flush toilets (I'm not sure what the correct terminology is). The other toilets in the house work fine, it's just the toilet in the main bathroom that is proving to be a problem. I figured that there must be something in the line that is causing the problem, something that isn't quite dislodged but is becoming dislodged with each flush. The amount of water entering the bowl seems to be about right, as does the force of the water entering the bowl. It's just that that vortex that usually forms as the water is swirling around doesn't form, and the water doesn't "flush" the way the other bowls in the house do. I don't believe that it's a problem that will require major repairs, if at all, but I will defer to the expertise of more knowledgeable people on this matter. Thanks for your help.

Sounds like you may have something caught up in the throat of the bowl.
To test, AND THIS IS Important, Take the lid off the tank so that you can push the flapper down if it starts to over flow. Now load up the bowl with paper and flush, keeping your hand near the flapper just in case. Do this 4 or 5 times. Use plenty of paper, most of a roll. If there is anything still caught down there the paper will catch on it and start to back up. If that happens push down on the flapper to stop the water from the tank from overflowing the bowl and click on back for instructions auguring out the bowl. Good luck. Tom